Did Michael Sullivan Sr. really believe he could trade with Capone?

In the movie Road to Perdition, Michael Sullivan Sr. (after this I shall write just Mike to represent him as he was called by that name in the movie and also to remove confusion with his son) asked Frank Nitti for work and was refused. Then, Harlen Maguire tried to assassinate Mike but failed. Realising that even Capone's men were against him, he tried to rob their money by saying:

I have to make Capone give up Connor. There's one thing Chicago loves more than anything... and that's their money. They've got it in banks all over the state. We have to find it and take it.

So, my question is what was in Mike's mind? Did he think that robbing Capone of his money would compel Capone to hand Connor over to him? Why couldn't Capone kill his money's robber? Why didn't Mike think about taking that? I mean the rivalry with Capone could prove lethal to him, wasn't it obvious that stealing his money would have ugly consequences?